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I've skimmed Programming in Lua, I've looked at the Lua Reference.
However, they both tells me this function does this, but not how.
When reading SICP, I got this feeling of: "ah, here's the computational model underlying scheme"; I'm trying to get the same sense concerning Lua -- i.e. a concise description of it's vm, a "how" rather than a "what".
Does anyone know of a good document (besides the C source) describing this?
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Since 2003, with the release of Lua 5.0, Lua uses a register-based virtual machine.
The Lua compiler uses no intermediate representation. It emits instructions for the virtual machine “on the fly” as it parses a program. Nevertheless, it does perform some optimizations. For instance, it delays the generation of code for base expressions like variables and constants.
Lua bytecode instructions are 32-bits in size. All instructions have an opcode in the first 6 bits. Instructions can have the following fields: 'A' : 8 bits 'B' : 9 bits 'C' : 9 bits 'Ax' : 26 bits ('A', 'B', and 'C' together) 'Bx' : 18 bits ('B' and 'C' together) 'sBx' : signed Bx.
You might want to read the No-Frills Intro to Lua 5(.1) VM Instructions (pick a link, click on the Docs tab, choose English -> Go).
I don't remember exactly where I've seen it, but I remember reading that Lua's authors specifically discourage end-users from getting into too much detail on the VM; I think they want it to be as much of an implementation detail as possible.
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